FIGURE 1.

CB₁R receptor expression and function in rat skeletal muscle arterioles. A, relaxations induced in rat gracilis arteriole segments by the CB₁R agonist WIN 55212 (1 μm) and by the endothelial relaxant Ach (10 μm) as well as the effects of de-endothelization (5–5 segments) are shown. Values were calculated as percent change of diameter compared with control. Mean ± S.E. values are shown. The asterisk indicates significant change of agonist-induced tone in response to inhibitor treatment (p < 0.05). B, shown is gel electrophoresis of the mRNA amplicons and relative quantification of mRNA expression. Messenger RNA expression of CB₁R (Cnr1 gene) was normalized to glyceraldehyde-3-phosphate dehydrogenase (Gapdh, n = 4). Grac. a., gracilis arterioles. C, shown is Western blot detection of CB₁R protein from tissue homogenates. Expression of CB₁R protein in rat aorta and gracilis arterioles was quantitatively detected by densitometry (n = 4) of HRP-induced fluorescence. D, immunohistochemical localization of the CB₁R protein (arrows) in rat gracilis arterioles and in mouse gracilis vessels is shown. No staining was detected in CB₁R knock-out (−/−) mice. Left bar, 50 μm. Bars in middle and right, 100 μm.